Due to busy pace in modern living, indoor exercises have grown extremely popular. Among them, the exercise bicycle has become one of the most popular exercise equipments. To consume the energy of the user, traditional exercise bicycles adopt the following braking means:
Friction Type:
Most traditionally used, it mainly adopts such material as woolen rug to impede the rotor by direct friction, thus achieving the braking purpose. The merits are simple construction and low cost. However, the drawbacks include (1) The frictional force at startup and low speed is greater than that in high speed operation, resulting in an unsmooth impedance characteristic, which causes an unsmooth feeling at restart from pause in the exercise process; (2) The braking force can not be conveniently adjusted by an electronic circuit; (3) The amount of exercise can not be precisely measured.
Later, design of various braking devices in different constructions came out in succession.
Vortex Braking Device:
A magnetic force control system is used to provide control without a dynamo. The merits are (1) lower manufacturing cost as compared to those with a dynamo and (2) no disturbance from magnetic noise. However, to produce the braking force, it requires either (1) external power control or (2) mechanical approach to alter the braking magnetic force. The drawbacks are in the former case (1) danger of electric shock by leakage or trip off by the electrical wire, and in the latter case (2) slow response time, high cost, and sometimes the mechanical noise of the control mechanism.
Dynamo Braking Device:
All merits are derived from a built-in dynamo in the device: (1) free from battery or external power control; (2) The amount of electricity generated is directly proportional to the consumption of calories by user, which can be precisely converted to show the amount of exercise for user's reference; (3) The amount of braking can be directly controlled by the electrical signal, which enables more entertaining exercise process when coupled with appropriate man-machine interface by electronic circuits. However, the drawbacks include (1) high cost; (2) Inverting magnetic force by magnetic poles produces noise; (3) Magnetized dynamos exhibit such problems as nonlinearity and insufficient power; (4) Common permanent magnet dynamos with few magnetic poles exhibit such problems as dead starting angles.
Vortex Braking Device Incorporated With a Dynamo:
It shares the merits of both vortex and dynamo braking devices. However, soaring cost inhibits its popular use.